Evolution

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SMALL BUT DEADLY The potent toxin epibatidine was first discovered in 1974, when it was isolated from the skin of the phantasmal poison frog, Epipedobates anthonyi (one shown).

R. Tarvin/University of Texas at Austin

PRIMITIVE FISH Polypterus (shown) is a living member of a large group of vertebrates called ray-finned fishes. New evidence suggests that ray-finned fishes arose about 360 million years ago, after a major extinction event, then their diversity exploded.

Matt Friedman/Univ. of Michigan

RHINO TWILIGHT As woolly rhinos dwindled to extinction, their odds of having odd ribs attached to their neck bones may have risen. Here, one of the creatures is shown in a wall painting at Chauvet-Pont d’Arc Cave in southern France.